Earle F. Philhower, III
44cd697b29
Fixes #472 Instead of using interrupts, explicitly call the IRQ handler dueing Serial read/peek/available calls. Add to keywords.txt for syntax hilighting. Add poll calls in the SerialUART::write-like calls (write, flush, etc.) Really remove division from IRQ routines/
47 lines
1.6 KiB
ReStructuredText
47 lines
1.6 KiB
ReStructuredText
Serial Ports (USB and UART)
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===========================
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The Arduino-Pico core implements a software-based Serial-over-USB port
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using the USB ACM-CDC model to support a wide variety of operating
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systems.
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``Serial`` is the USB serial port, and while ``Serial.begin()`` does allow
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specifying a baud rate, this rate is ignored since it is USB-based.
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(Also be aware that this USB ``Serial`` port is responsible for resetting
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the RP2040 during the upload process, following the Arduino standard
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of 1200bps = reset to bootloader).
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The RP2040 provides two hardware-based UARTS with configurable
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pin selection.
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``Serial1`` is ``UART0``, and ``Serial2`` is ``UART1``.
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Configure their pins using the ``setXXX`` calls prior to calling ``begin()``
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.. code:: cpp
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Serial1.setRX(pin);
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Serial1.setTX(pin);
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Serial1.begin(baud);
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The size of the receive FIFO may also be adjusted from the default 32 bytes by
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using the ``setFIFOSize`` call prior to calling ``begin()``
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.. code:: cpp
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Serial1.setFIFOSize(128);
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Serial1.begin(baud);
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The FIFO is normally handled via an interrupt, which reduced CPU load and
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makes it less likely to lose characters. However, the FIFO introduces up
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to 32 bit-times of delay before serial data is available to the application.
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For applications where this is an issue (i.e. very low baud), use
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``setPollingMode(true)`` before calling ``begin()``
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.. code:: cpp
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Serial1.setPollingMode(true);
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Serial1.begin(110)
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For detailed information about the Serial ports, see the
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Arduino `Serial Reference <https://www.arduino.cc/reference/en/language/functions/communication/serial/>`_ .
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